Magnesia spinel brick for refining new energy motor silicon steel and preparation method thereof

Abstract

The invention discloses a magnesia spinel brick for new energy motor silicon steel refining and a preparation method thereof, 75-80 parts of macrocrystalline magnesia material, 10-15 parts of zirconium material and 5-8 parts of composite additive are used as raw materials, and an additional binding agent accounts for 2.5-3.5% of the total weight of the raw materials; the magnesium spinel brick is prepared through the steps of burdening, mixing, vibration pressure forming, drying and the like, in a high-temperature use environment, an in-situ reaction is carried out to generate a main product which is a complex-phase solid solution of MgAlON and Al2OC-AlNss, and the magnesium spinel brick not only has excellent corrosion resistance of nitride, but also has the advantages of high thermal conductivity, low thermal expansion coefficient, good impact resistance and the like of carbide, and is suitable for industrial production. The use performance of the magnesia spinel brick is obviously improved, and meanwhile, the porosity is reduced; the magnesium spinel brick is simple in production process, few in used raw materials and simple in technological process, the magnesium spinel brick which is high in strength, free of inclusion, stable in thermal shock performance and the like can be produced, the using effect is more excellent, and production of silicon steel for new energy motors is met.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials for silicon steel refining, and specifically relates to a magnesium spinel brick for new energy motor silicon steel refining and a preparation method thereof. Background Art

[0002] With the development of my country's new energy vehicle industry, the sales of pure electric vehicles will reach 6.685 million units in 2023, and the sales of plug-in hybrid vehicles will reach 2.804 million units. As the core material of new energy motors, the demand for high-end silicon steel products for motors will become more and more urgent. Non-oriented silicon steel with low iron loss, high magnetic induction and high efficiency for motors, thin-gauge ultra-low iron loss and high magnetic induction oriented silicon steel, and high silicon steel for medium and high frequency energy-saving electrical appliances are the development direction of the electrical steel industry. The performance requirements of low iron loss and high magnetic induction for silicon steel for new energy motors determine that the content of nitrogen and sulfur in silicon steel must be controlled at extremely low levels. If you want to remove impurities in silicon steel efficiently and quickly, you must use the RH furnace refining system.

[0003] The RH off-furnace refining system is a secondary refining process equipment for molten steel used to produce high-quality steel. The entire molten steel metallurgical reaction is carried out in a vacuum tank with a refractory lining. The vacuum tank is an integral welded steel body, the interior of which is protected by refractory masonry. Magnesium spinel bricks are the working layer, which is in direct contact with the molten steel and is an important part of the entire vacuum system. The use status of magnesium spinel bricks directly affects the entire refining system. The performance requirements of low iron loss and high magnetic induction for silicon steel used in new energy motors put forward the requirements of ultra-purity and ultra-low carbon, ultra-low sulfur and ultra-low nitrogen for silicon steel, which inevitably requires precise control of the total content of C, P, S, N, H and O in the steel. In addition, it is necessary to avoid non-metallic inclusions in the steel to improve the purity of the molten steel, which has become the core of advanced steel metallurgical technology.

[0004] Refractory materials are the basic materials to ensure the technological development of the steel and metallurgical industry. Under the general situation of vigorously developing high-performance silicon steel technology, the service environment of magnesium spinel bricks for RH furnaces has become particularly harsh. They must not only be able to withstand the erosion of high-speed molten steel, but also have good high-temperature strength, excellent thermal shock resistance, and good volume stability under vacuum. In addition, they are required to be carbonized and high-purity to avoid carburization of lining materials into molten steel during service, produce non-metallic inclusions, and ensure high resistance to slag erosion. Traditional magnesium spinel bricks can hardly meet the requirements of refining high-performance silicon steel. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a magnesium spinel brick for refining silicon steel for new energy motors and a preparation method thereof. The raw materials used are relatively small and the process is simple. Magnesium spinel bricks with better properties such as high strength, no inclusions, and stable thermal shock resistance can be produced. The use effect is more superior to meet the production of silicon steel for new energy motors.

[0006] The technical solution adopted by the present invention is: a magnesium spinel brick for refining silicon steel for new energy motors, comprising the following raw material components and the weight portions added: 75-80 parts of large crystalline magnesia sand material, including 14-18 parts of magnesia sand with a particle size of 5-3mm, 30-35 parts of magnesia sand with a particle size of 3-1mm, 15-20 parts of magnesia sand with a particle size of 1-0.5mm, 5-12 parts of magnesia sand with a particle size of 0.5-0mm, and 3-6 parts of magnesia sand with a particle size of 320 mesh; 10-15 parts of zirconium material with a particle size of <180 mesh, 5-8 parts of composite additives with a particle size of ≤0.5mm, and an external binder accounting for 2.5-3.5% of the total weight of the raw material.

[0007] The content of magnesium oxide in the large crystalline magnesia material is greater than 97wt%.

[0008] The content of zirconium oxide in the zirconium material is greater than 98.5 wt%.

[0009] The composite additive comprises metal aluminum powder, silicon nitride powder and ultrafine graphite powder.

[0010] The carbon content in the graphite powder is greater than 95 wt%.

[0011] The aluminum content in the metal aluminum powder is greater than 98.5 wt%.

[0012] The binder is one or a combination of resin, pulp waste liquid, phosphoric acid and phosphate.

[0013] A method for preparing magnesium spinel bricks for refining silicon steel for new energy motors comprises the following steps: Step 1: Ingredients: weigh the raw materials according to the formula requirements; Step 2: Mixing: Premix the granular aggregate first, add the binder after mixing evenly, continue mixing evenly, add the fine powder matrix material, and continue mixing until the raw materials are uniform; Step 3: Molding: Weigh the mixed raw materials according to the quality requirements, add them into the mold, and use vibration and uniform material pulling on all sides to form them on a 1000-ton friction brick press or hydraulic press. The molding pressure is greater than 20Mpa. Step 4: Drying: The formed bricks are baked in a drying kiln at 150-200°C for 12-24 hours to dehydrate.

[0014] The present invention uses large-crystal magnesia sand material, zirconium material and composite additives as raw materials, contacts nitrogen in the high-temperature use environment of RH furnace refining, and generates in-situ reaction to form a composite solid solution material whose main products are MgAlON and Al2OC-AlNss, wherein the MgAlON reinforcement phase fills and divides the pores, inhibits slag penetration, and improves the corrosion resistance of the magnesium spinel brick material. Its low linear expansion coefficient and high thermal conductivity improve the thermal shock stability of the material during service; the Al2OC-AlNss solid solution has the advantages of high melting point, good high-temperature stability and excellent corrosion resistance, as well as high thermal conductivity, low thermal expansion coefficient and good thermal shock resistance. Al2OC-AlNss is basically not wetted by molten slag at high temperature, so it can significantly improve the composite anti-slag corrosion performance. MgAlON and Al2OC-AlNss solid solution composite refractory materials have not only the excellent corrosion resistance of nitrides, but also the advantages of high thermal conductivity, low thermal expansion coefficient, good impact resistance, etc. of carbides. The production amount and distribution are uniform, thereby improving the mechanical strength of the composite material, while taking into account its slag corrosion resistance and melt erosion resistance at high temperatures.

[0015] The present invention uses large crystal magnesia material to increase the size of periclase crystals in the magnesia, which can reduce the reaction activity of magnesium oxide with carbon and slag, and is beneficial to improving the slag resistance and service life of the refractory material.

[0016] The beneficial effects of the present invention are: The magnesium spinel brick of the present invention has reasonable proportions of various raw materials, can react after high temperature to generate a multiphase solid solution with MgAlON and Al2OC-AlNss as main products, has uniform and reasonable particle size distribution, can fill the gaps between particles very well, has controlled high-temperature products, and has no harmful products generated. It has the advantages of excellent corrosion resistance of nitrides, high thermal conductivity of carbides, low thermal expansion coefficient, good impact resistance, etc., thus significantly improving the use performance of magnesium spinel bricks and reducing porosity at the same time; adopting the method of uniformly pulling and feeding materials on all sides and vibrating and pressurizing molding, the molding density of the brick blank is improved, and the use strength of the magnesium spinel brick is further improved; the production process is simple, the equipment requirements are low, the production cost is relatively low, and large-scale preparation can be carried out. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0018] A magnesium spinel brick for refining silicon steel for new energy motors comprises the following raw material components and the weight proportions added: 80 parts of magnesium oxide materials, of which 15 parts are of particle size of 5-3 mm, 30 parts are of particle size of 3-1 mm, 18 parts are of particle size of 1-0.5 mm, 11 parts are of particle size of 0.5-0 mm, and 6 parts are of 320 mesh; 11 parts of zirconium oxide with particle size of less than 180 mesh, 3 parts of metal aluminum powder, 1 part of silicon nitride powder, 3 parts of ultrafine graphite powder, and a phenolic resin binder is added, accounting for 2.7% of the total weight of the raw material.

[0019] A method for preparing magnesium spinel bricks for refining silicon steel for new energy motors comprises the following steps: Step 1: Ingredients: weigh the raw materials according to the formula requirements; Step 2: Mixing: Premix the granular aggregate first, add the binder after mixing evenly, continue mixing evenly, add the fine powder matrix material, and continue mixing until the raw materials are uniform; Step 3: Molding: Weigh the mixed raw materials according to the quality requirements, add them into the mold, and use vibration and uniform material pulling on all sides to form them on a 1000-ton friction brick press or hydraulic press. The molding pressure is greater than 20MPa. Step 4: Drying: The formed bricks are baked in a drying kiln at 150-160°C for 22-24 hours to dehydrate. Example 2

[0020] A magnesium spinel brick for refining silicon steel for new energy motors comprises the following raw material components and the weight proportions added: 77 parts of magnesium oxide materials, of which 16 parts are of particle size of 5-3 mm, 32 parts are of particle size of 3-1 mm, 16 parts are of particle size of 1-0.5 mm, 10 parts are of particle size of 0.5-0 mm, and 3 parts are of particle size of 320 mesh; 13 parts of zirconium materials with particle size of less than 180 mesh, 2 parts of metal aluminum powder, 2 parts of silicon nitride powder, 2 parts of ultrafine graphite powder, and an additional pulp waste liquid binder accounts for 2.5% of the total weight of the raw material.

[0021] A method for preparing magnesium spinel bricks for refining silicon steel for new energy motors comprises the following steps: Step 1: Ingredients: weigh the raw materials according to the formula requirements; Step 2: Mixing: Premix the granular aggregate first, add the binder after mixing evenly, continue mixing evenly, add the fine powder matrix material, and continue mixing until the raw materials are uniform; Step 3: Molding: Weigh the mixed raw materials according to the quality requirements, add them into the mold, and use vibration and uniform material pulling on all sides to form them on a 1000-ton friction brick press or hydraulic press. The molding pressure is greater than 20MPa. Step 4: Drying: The formed bricks are baked in a drying kiln at 160-180°C for 18-20 hours for dehydration. Example 3

[0022] A magnesium spinel brick for refining silicon steel for new energy motors comprises the following raw material components and the weight proportions added: 80 parts of magnesium oxide materials, of which 14 parts are of particle size of 5-3 mm, 33 parts are of particle size of 3-1 mm, 20 parts are of particle size of 1-0.5 mm, 5 parts are of particle size of 0.5-0 mm, and 5 parts are of particle size of 320 mesh; 10 parts of zirconium materials with particle size less than 180 mesh, 3 parts of metal aluminum powder, 2 parts of silicon nitride powder, 3 parts of ultrafine graphite powder, and an additional phosphate binder accounts for 3% of the total weight of the raw materials.

[0023] A method for preparing magnesium spinel bricks for refining silicon steel for new energy motors comprises the following steps: Step 1: Ingredients: weigh the raw materials according to the formula requirements; Step 2: Mixing: Premix the granular aggregate first, add the binder after mixing evenly, continue mixing evenly, add the fine powder matrix material, and continue mixing until the raw materials are uniform; Step 3: Molding: Weigh the mixed raw materials according to the quality requirements, add them into the mold, and use vibration and uniform material pulling on all sides to form them on a 1000-ton friction brick press or hydraulic press. The molding pressure is greater than 20MPa. Step 4: Drying: The formed bricks are baked in a drying kiln at 180-200°C for 12-16 hours for dehydration.

[0024] The main performance indicators of the magnesium spinel bricks prepared in Examples 1-3 are shown in the following table:

[0025] The parts of the present invention that are not described in detail are prior art. The above embodiments will help relevant persons in the art to further understand the present invention, but do not limit the present invention in any form. Without departing from the scope of the present invention defined by the attached claims, various changes in form, details or equivalents made using the present invention are all within the protection scope of the present invention.

Claims

1. A magnesium spinel brick for refining silicon steel for new energy motors, characterized in that: The invention comprises the following raw material components and the weight proportions added: 75-80 parts of large crystalline magnesia material, including 14-18 parts of magnesia with a particle size of 5-3mm, 30-35 parts of magnesia with a particle size of 3-1mm, 15-20 parts of magnesia with a particle size of 1-0.5mm, 5-12 parts of magnesia with a particle size of 0.5-0mm, and 3-6 parts of magnesia with a particle size of 320 mesh; 10-15 parts of zirconium material with particle size less than 180 mesh, 5-8 parts of composite additive with particle size ≤0.5mm, and the added binder accounts for 2.5-3.5% of the total weight of the original material.

2. The magnesium spinel brick for refining silicon steel for new energy motor according to claim 1 is characterized in that: The content of magnesium oxide in the large crystalline magnesia material is greater than 97wt%.

3. The magnesium spinel brick for refining silicon steel for new energy motor according to claim 1 is characterized in that: The content of zirconium oxide in the zirconium material is greater than 98.5 wt%.

4. The magnesium spinel brick for refining silicon steel for new energy motor according to claim 1 is characterized in that: The composite additives include metallic aluminum powder, silicon nitride powder and ultrafine graphite powder.

5. The magnesium spinel brick for refining silicon steel for new energy motor according to claim 4 is characterized in that: The carbon content in the graphite powder is greater than 95wt%.

6. The magnesium spinel brick for refining silicon steel for new energy motor according to claim 4 is characterized in that: The aluminum content in the metal aluminum powder is greater than 98.5wt%.

7. The magnesium spinel brick for refining silicon steel for new energy motor according to claim 1 is characterized in that: The binder is one or a combination of resin, pulp waste liquid, phosphoric acid and phosphate.

8. The method for preparing a magnesium spinel brick for refining silicon steel for new energy motors according to claim 1, characterized in that: The following steps are involved: Step 1: Ingredients: weigh the raw materials according to the formula requirements; Step 2: Mixing: Premix the granular aggregate first, add the binder after mixing evenly, continue mixing evenly, add the fine powder matrix material, and continue mixing until the raw materials are uniform; Step 3: Molding: Weigh the mixed raw materials according to the quality requirements, add them into the mold, and use vibration and uniform material pulling on all sides to form them on a 1000-ton friction brick press or hydraulic press. The molding pressure is greater than 20Mpa. Step 4: Drying: The formed bricks are baked in a drying kiln at 150-200°C for 12-24 hours to dehydrate.

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